Locally adaptive Nakagami-based ultrasound similarity measures

The derivation of statistically optimal similarity measures for intensity-based registration is possible by modeling the underlying image noise distribution. The parameters of these distributions are, however, commonly set heuristically across all images. In this article, we show that the estimation of the parameters on the present images largely improves the registration, which is a consequence of the more accurate characterization of the image noise. More precisely, instead of having constant parameters over the entire image domain, we estimate them on patches, leading to a local adaptation of the similarity measure. While this basic idea of creating locally adaptive metrics is interesting for various fields of application, we present the derivation for ultrasound imaging. The domain of ultrasound is particularly appealing for this approach, due to the inherent contamination with speckle noise. Furthermore, there exist detailed analyses of suitable noise distributions in the literature. We present experiments for applying a bivariate Nakagami distribution that facilitates modeling of several scattering scenarios prominent in medical ultrasound. Depending on the number of scatterers per resolution cell and the presence of coherent structures, different Nakagami parameters are required to obtain a valid approximation of the intensity statistics and to account for distributional locality. Our registration results on radio-frequency ultrasound data confirm the theoretical necessity for a spatial adaptation of similarity metrics.     

Investigations on mufflers for internal combustion engines

This paper deals with experimental studies on reactive types of muffler—and their combinations with absorption types—in order to determine their noise attenuation characteristics. Tests were carried out on a test rig, with a loudspeaker as the input source, as well as on a four cylinder diesel engine. The frequency spectra of attenuation levels, obtained experimentally, were compared with corresponding theoretical predictions. In addition, the effect on the performance of the engine itself was studied.The results showed, in general, a fairly good agreement between experimental results from test rig and theoretical predictions in the frequency range for which the latter is valid. The attenuation levels obtained from the mufflers fitted on the engine were, in general, lower. The effect on the performance of the engine was marginal. It was seen that the combination mufflers offer a good solution when high noise attenuation is desired.     

Solid-phase synthesis of γ-AApeptides using a submonomeric approach

The solid-phase synthesis of γ-AApeptides using a novel submonomeric approach that utilizes an allyl protection is reported. The strategy successfully circumvents the necessity of preparing γ-AApeptide building blocks in order to prepare γ-AApeptide sequences. This method will maximize the potential of developing chemically diverse γ-AApeptide libraries and thereby facilitate the biological applications of γ-AApeptides in the future.     

A Stereodivergent Approach to the Synthesis of gem-Diborylcyclopropanes

We report a designed stereodivergent strategy for the synthesis of gem-diborylcyclopropanes. The reaction provides a highly modular approach to prepare cyclopropane ring variants bearing gem-(Bpin,Bpin), gem-(Bpin,Bdan), and gem-(Bpin,BF₃K), with outstanding levels of stereocontrol. This was achieved by diastereoselective Pd-catalyzed cyclopropanation reactions of gem-diborylalkenes with α-diazoarylacetates and α-diazoaryl-trifluoromethyl. The key to the success of this general protocol was the diastereoselective trifluorination reaction of gem-diborylcyclopropanes, followed by the stereospecific interconversion of the trifluoroborate salts into the Bdan group.     

Characterization of nanohybrid membranes for direct methanol fuel cell applications

A series of sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (S-PPO) and sulfonated poly(ether ether ketone) (S-PEEK) at various sulfonation degrees were prepared and characterized for their degree of sulfonation, water uptake, ion exchange capacity, proton conductivity and methanol permeability. Based on the obtained results, the optimum samples were determined and subsequently blended together at different compositions. A single glass transition temperature (T_g) was determined for all blend samples, which was attributed to the presence of sulfonate groups on polymer backbones resulting in the formation of electrostatic cross-linking besides phenyl–phenyl interactions. Moreover, the molecular level of mixing in blends was verified through WAXS patterns. According to the membrane selectivity and hydrolytic stability measurements, 75 wt.% of S-PPO and 25 wt.% of S-PEEK was selected as the optimum composition. Afterwards, different amounts of an organically modified montmorillonite (MMT) were incorporated into the predetermined optimum composition matrices to reduce the methanol permeability of the resulted nanocomposite proton exchange membranes. The XRD patterns of nanocomposites revealed the exfoliated microstructure of the clay nanolayers in the polymeric matrices. Transport property measurements of nanohybrid membranes showed that the maximum selectivity parameter of 75 wt.% S-PPO/25 wt.% S-PEEK composition appeared in the presence of 1.5 wt.% of MMT, which is 1.53 times higher than the corresponding value for Nafion^® 117. The DMFC single cell test of the optimum nanohybrids membrane at 5 M methanol feed showed an open circuit voltage of 0.77 V and maximum power density of 135 mW cm^? 2 in comparison with 0.67 V and 108 mW cm^? 2 for Nafion^® 117, respectively. Fabricated nanohybrid membranes, thanks to their high selectivity, desirable transport properties and tenability, could be considered as promising polyelectrolytes for direct methanol fuel cell applications.     

Enantioselective Crystallization of Chiral Inorganic Crystals of ϵ-Zn(OH)2 with Amino Acids

Many inorganic materials can form crystals, but little is known about their enantioselective crystallization. Herein, we report on the enantioselective crystallization of ϵ-Zn(OH)₂ (Wulfingite) chiral crystals by using amino acids. Crystals of ϵ-Zn(OH)₂ were crystallized from supersaturated sodium hydroxide and zinc nitrate aqueous solutions in the presence of l - or d -arginine. All of the chiral measurements, such as selective chiral adsorption by circular dichroism (CD), chiral chromatography, and polarimetry measurements, clearly show chiral discrimination during the crystallization of ϵ-Zn(OH)₂. In addition, a new method has been developed for identifying chirality in crystals by using electron paramagnetic resonance (EPR). Although the values of chiral induction of the ϵ-Zn(OH)₂ crystals obtained are somewhat low, these values are still significant because they demonstrate that enantioselectivity during the crystallization of chiral inorganic crystals with chiral additives can be achieved. The method can be applied to many chiral inorganic systems. Understanding and controlling the crystallization of chiral inorganic crystals is important for gaining knowledge on the interaction of chiral molecules with inorganic surfaces. This knowledge can lead to an understanding of basic scientific questions such as the evolution of homochirality in biomolecules and the development of chiral inorganic crystals for a variety of purposes such as asymmetric catalysis and optical applications.     

Synthesis,spectral and antimicrobial activity studies of o-aminoacetophenone o-hydroxybenzoylhydrazone complexes

Coordination compounds of Mn^II, Co^II, Ni^II, Cu^II, Zn^II, Cd^II and Hg^II ions with o-aminoacetophenone o-hydroxybenzoylhydrazone (AAOHBH) were synthesized and characterized by elemental analyses, molar conductivity, magnetic moments (at ca. 25°C) and spectral (i.r., u.v., n.m.r. and m.s.) studies. The i.r. spectra show that the ligand acts in a monovalent bidentate, neutral bidentate and/or neutral tridentate fashion, depending on the metal salt used and the reaction medium. Tetrahedral structures are proposed for both Co^II and Ni^II complexes and square planar for Cu^II complexes on the basis of magnetic and spectral evidence. The complex formation in solution was investigated potentiometrically and spectrophotometrically. Spectral studies in solution show that the ligand can be used for the microdetermination of Co^II ion within a metal concentration up to 46.3p.p.m. The electrical conductivity of AAOHBH and its metal complexes was determined. The tendency of AAOHBH to form complexes with Co^II, Ni^II, Cu^II, Cd^II and Hg^II ions in 50% aqueous-dioxane was studied by pH measurements.The antimicrobiol activity of AAOHBH and its complexes derived from Co^II, Ni^II and Cu^II illustrates that the Ni^II complex seems to be inert towards Escherichia coli and Bacillus subtilis. The antimicrobial activity of the Cu^II complex was higher against E. coli and lower against B. subtilis than the corresponding organic ligand. The Co^II complex has the same activity as the organic ligand against E. coli.